1. Field of the Invention
The present invention relates to a three dimensional display device, and in particular, to an autostereoscopy-type three dimensional display device using a parallax barrier.
2. Description of the Related Art
Generally, three dimensional display devices supply different views to the left and right eyes of a user such that the user can have the depth perception of the viewed images. The three dimensional display devices may be classified into a stereoscopic display device where the user should wear viewing aids, such as polarizing glasses, and an autostereoscopic display device where the user can see the desired three dimensional images without wearing such viewing aids.
A common autostereoscopic display utilizes an optical separation element (or optical isolation element), such as a lenticular lens, a parallax barrier, or a microlens array, to spatially separate or isolate the left-eye image part and the right-eye image part displayed at an image display unit in the directions of the left and right eyes of the user, respectively.
In particular, the parallax barrier may be formed with a liquid crystal shutter utilizing a transmission type of liquid crystal display, and in this case, it may be converted between a two dimensional mode and a three dimensional mode. Thus the parallax barrier can be applied to laptop computers or cellular phones easily.
Sets of red (r), green (g), and blue (b) sub-pixels are alternately and repeatedly arranged in the image display unit.
A left image signal or a right image signal is input into electrodes corresponding to the sub-pixels. Generally these image signals are alternately and repeatedly input thereto according to an array of the sub-pixels.
The parallax barrier includes stripe-shaped light interception portions and light transmission portions. The light transmission portions are arranged such that each of the light transmission portions corresponds to at least two of the pixels.
With the above structure, the right-eye image light beams emitted from the sub-pixels for the right eye are transmitted through the light transmission portions toward the right eye of the user while being intercepted by the light interception portions in the direction of the left eye of the user.
The left-eye image light beams emitted from the sub-pixels for the left eye are transmitted through the light transmission portions toward the left eye of the user while being intercepted by the light interception portions in the direction of the right eye of the user.
Accordingly, the left and right images respectively reach the left and right eyes so that the user can see the desired three dimensional images.
When the parallax barrier is formed with a liquid crystal shutter, the distance between the three dimensional display device and the user (view distance) should be maintained at about 300˜400mm for the user to see the three dimensional images.
But when the three dimensional display device is adapted to small-sized devices such as cellular phones and personal digital assistants (PDAs), according to the characteristics of the small-sized devices the view distance may be increased.
Accordingly, the view distance should be reduced for the user to see the three dimensional images with small-sized devices. Thus, efforts to optimize the view distance by reducing the distance between the image display plane formed in the image display unit and image separation plane formed in the parallax barrier have been undertaken.
With one of these efforts, the view distance can be reduced by reducing the thickness of the glass substrates of the flat panel display device (i.e., a liquid crystal display device) and the liquid crystal shutter used as a parallax barrier.
But this method has some limitations due to the minimum thickness of the glass substrates and some problems in the manufacturing processes.
Meanwhile, other efforts to reduce the view distance have been made, such as separating the left-eye image and the right-eye image by pixel units, but not by sub-pixel units.
In this case, color dispersion may occur such that each of the light beams from red, green, and blue sub-pixels is not gathered in a certain position but is dispersed.